The present invention relates to the field of catheterization of a lumen within the human body, particularly the vasculature. Even more particularly, the invention will have application to the manufacture and construction of balloon catheters used in angioplasty.
Angioplasty procedures have gained wide acceptance as an efficient and effective method for treating certain types of vascular disease. In particular, angioplasty is widely used for stenoses in the coronary arteries, although it is also used for the treatment of stenoses in other parts of the vascular system.
The most widely used form of angioplasty makes use of a dilatation balloon catheter to treat a stenosis and thereby reestablish an acceptable blood flow through the artery. The dilatation catheter includes an elongated tubular shaft and an inflatable balloon carried at a distal end of the shaft. In operation, the catheter is inserted through a guide catheter which has been previously introduced into a patient""s vascular system from a location remote from the heart (e.g., femoral artery). The proximal end of the guide catheter remains outside the patient, while the distal end of the guide catheter is positioned at the coronary artery ostium. A dilatation catheter is introduced into the proximal end of the guiding catheter and advanced to the distal end of the guide catheter. Then, by using fluoroscopy, the physician guides the dilatation catheter the remaining distance through the vascular system until the balloon is positioned across the stenosis.
Fluoroscopy, the use of radiographic images to view a catheter""s position and progress through a patient""s vasculature, is essential in allowing the interventional radiologist to accomplish the desired results during diagnostic procedures such as angiography and treatment procedures such as angioplasty. Catheters are made visible through the use, for example, of radiopaque materials impregnated in the catheter materials, or radiopaque marker bands around the catheters. Radiopaque contrast solution, when injected into patient vasculature at the distal end of the catheter, permits the physician to see otherwise virtually invisible vasculature and chart out the desired course of the catheter being guided to the diagnostic or treatment site. Accordingly, the simple and safe injection of contrast media is a basic necessity for all angiographic procedures. Virtually every case of angiographic and other interventional radiological intervention requires multiple contrast injections to visualize the patient""s peripheral vasculature, coronary vessels, bypass grafts, or other treatment site vasculature.
The typical practice of physicians in delivering contrast media is to hand inject contrast media down the lumen of a catheter using a syringe connected to an angiographic manifold. The hand injection process requires the physician to manipulate at least one, if not multiple, stopcock valves on the manifold to allow them to aspirate contrast into the syringe and then inject it into the patient. Because of the multiple stopcocks and syringes that must be manipulated, the procedure requires two hands and typically about nine separate steps to perform. This procedure is cumbersome and time consuming. In addition, the inconvenience of existing methods of delivery may force the physician""s attention away from the catheter which is being steered through the patient vasculature.
The present invention reduces the hand injection of contrast to one simple step, the squeeze of a small pump located on or near the manifold. Because of its ease of operation, a device of the instant invention can be used to inject contrast during the placement of a catheter, providing the additional benefit of real-time assessment of catheter position as it is manipulated. Former methods of contrast fluid introduction were often too unwieldy to permit their use during catheter placement.
The present invention provides a parallel or alternate route for the injection of a fluid bolus, such as contrast solution, into a catheter during catheter placement, or during other aspects of interventional radiographic treatment or diagnosis. The former turning of various stopcocks or valves is replaced with the relatively simple squeeze of a pump bulb, which injects a bolus of the desired fluid into the catheter lumen. If more fluid is desired, the physician may simply make quick repeated injections of fluid in addition to that already injected.
The fluid inlet of an embodiment of the present invention is hooked up not only to the typical stopcocks of a manifold, but in addition to a fluid bypass tube running to a small pump. In a preferred embodiment, this pump is manually operated for simple and precise use. In one embodiment of the subject invention described below, the pump takes the form of a squeezable bulb that will eject fluid when squeezed, and when released, springs back into its original shape, drawing more fluid from the fluid source.
In a preferred embodiment, the outlet valve of the pump bulb, in addition to having the property of being a one-way valve, also has a cracking or threshold pressure. This cracking pressure is the pressure gradient between the supply side of the valve to the destination side of the valve, below which the valve will not allow flow through the valve. In other words, the pressure on the supply side of the valve must exceed the pressure on the destination side of the valve by an amount at least equal to the cracking pressure before the valve allows any fluid to flow through it. The use of a valve with a cracking pressure at the outlet valve of the pump bulb is preferred because this prevents the exit of contrast media from the pump bulb when the physician is aspirating fluid from the catheter lumen. If a valve without a cracking pressure was used, the pressure gradient created by the aspiration of the lumen would tend to suck contrast fluid at least in part from the pump bulb, rather than entirely from the catheter lumen as is intended. As long as the pressure gradient created by the aspiration of the catheter lumen is less than the cracking pressure of the outlet valve, the aspiration will not cause contrast fluid to escape from the pump bulb. Therefore, in a preferred embodiment, the cracking pressure of the pump bulb outlet valve is greater than the pressure gradient between the pump bulb and the catheter lumen caused by aspiration of the catheter lumen with a syringe.
One embodiment of the present invention has a pump bulb that ejects approximately 2 ml of contrast media with each complete squeeze of the pump bulb. Because the bulb cannot be completely evacuated by the squeeze administered by the operator, a preferred embodiment of the invention will have a pump bulb volume in excess of 2 ml. In an alternate embodiment of the present invention, the pump reservoir is a type of modified syringe, i.e., a cylindrical tube with a plunger for ejecting the fluid into the catheter shaft. In this embodiment, the pump reservoir has a compression spring that tends to push the plunger out of the reservoir to increase the volume of fluid in the syringe. The syringe style of pump reservoir may have volume indicator lines embossed or printed on the syringe and be transparent or translucent so that the volume of fluid in the reservoir may be viewed. This embodiment may be preferred for applications where more precise measurement of the volume of fluid injected into the catheter or tube is necessary, for example, if the invention is used to deliver therapeutic agents as opposed to contrast solution.
One embodiment of the present invention is a catheter in which a fluid injector or pump is an integral component of a catheter manifold. The present invention, however, may also be implemented as an auxiliary or add-on device which may be used with a variety of medical devices. For example, an embodiment of the instant invention may be used with any catheter that a physician prefers or finds most suitable for a particular application. The instant invention, when embodied in an add-on unit, may also be built with devices such as syringes, intravascular lines, and other devices using tubular conduit.
The use of a one-way valve at the pump bulb inlet and outlet valves are necessary because after the pump ball is squeezed to force fluid into the catheter lumen, and the pump bulb begins to expand again, the fluid that will fill the pump bulb must be supplied from the fluid supply vessel, and not from the delivery conduit leading to the catheter. If the fluid was allowed to flow back into the pump bulb, the fluid just delivered would be immediately aspirated back out of the catheter lumen by the low pressure created by the elastic expansion of the pump bulb. This, in turn, would cause fluid to be sucked into the catheter from the patient""s bloodstream. Of course, when the pump bulb was squeezed again, the contrast media or other fluid would not be delivered as expected at the catheter""s distal end.